Electric switches



3 Sheets-Sheet 1 Filed Aug. 18, 1959 7 Wye/v To)? Hdrv/l R. Scott a WWW M March 12, 1963 H.'.R'. SCOTT ELECTRIC SWITCHES 3 Sheets-Sheet 2 Filed Aug. 18, 1959 March 12, 1963 H. R. SCOTT 3,081,3

ELECTRIC SWITCHES Filed Aug. 18, 1959 3 Sheets-Sheet 3 age.

United States Patent Ofifice Patented Mar. 12, 1963 3,081,385 ELECTRIC SWITCHES Harold Richard Scott, London, England, assignor to The Birmingham Small Arms Company Limited, Birmingham, England, a company of Great Britain Filed Aug. 18, 1959, Ser. No. 834,613 2 Claims. (Cl. 200-67) This invention relates to electric switches of the kind in which a movable member is spring-loaded into a normally on or normally position and which carries a contact or contacts adapted to engage resiliently a contact or contacts mounted in th'e switch. In such switches a stop for the movable member (or a member which operates the movable member) is such that the resilient connection between the engaging contacts is compressed under the action of the spring acting upon the movable member. Electric switches of the kind referred to are frequently employed as limit switches.

It will be appreciated that in such switches replacement of the movable contact arm may be troublesome and inconvenient because one either has to compress the resilient connection between the contacts or, more usual, to hold back, away from the stop position, one or more other members through which the spring-loading is transmitted to the movable member.

It is an object of the present invention to provide a simple construction which facilitates replacement of the movable member.

According to this invention in an electric switch of the kind referred to there is provided a coupling between the movable member and another spring-loaded member, the coupling being such that preliminary engagement may be efiected between the movable member and the springloaded member without having to compress any springs but as final engagement is effected the movable member is automatically moved into its proper position, i.e. with the resilient connection between the contacts compressed.

In order that the invention may be fully understood and more readily carried into practice, I have caused to be appended hereunto drawings illustrating a constructional example thereof, wherein:

FIGURE 1 is a front view of a switch constructed in accordance with the invention, with a cover plate removed,

FIGURE 2 is a sectional side view taken on line AA of FIGURE 1,

FIGURE 3 is a similar view to FIGURE 1, with a part removed,

FIGURE 4 is a rear view of the switch with a cover plate removed,

FIGURE 5 is a side and end view of a detail,

FIGURE 6 is a side and end view of another detail, and

FIGURE 7 shows a tooth form on an enlarged scale.

Referring to the drawings, in the construction shown therein, the mechanism constituting a limit switch is mounted in a casing 1 and comprises a contact arm 3 pivotally mounted on a spindle 5 to which is secured a rocker 7 actuated by a spring-loaded roller slide 9 located in a pivotally mounted spring-loaded arm 11 con nected to an operating lever 13 pivoting about a shaft 15. The rocker 7 operates in conjunction with a pair of pivotally mounted spring-loaded latches 17 controlling the rocking movement imparted to the rocker 7 by the arm 11, and consequently to the contact arm 3 to bring the points 19 thereon into and out of contact with the fixed points 21.

On the spindle 5, adjacent to the contact arm 3, is formed on or securely fixed thereto a member 23 having three circumferentially disposed teeth 25 constituting projections and recesses with faces 27 inclined to the longitudinal axis of the spindle 5. The said projections and recesses are of substantially equal size, the projections being narrower at the top than at the bottom, with the faces 27 inclined at an angle of about 45.

On the contact arm 3, which is preferably fabricated as a moulding from a suitable insulating material, are formed three similar teeth 29 constituting projections and recesses with inclined faces 31, said teeth corresponding in size and shape to the aforesaid teeth 25 on the spindle 5. An aperture 33 in the arm 3 is adapted to engage with a cylindrical boss 35 formed on the member 23 for locating the interenga-ging teeth, and when the arm 3 is placed on the spindle 5, a threaded portion or stud 37 extending from the boss 35 protrudes beyond the outer surface of the arm 3 to accommodate a nut 39.

In order to replace the contact arm 3, it is only necessary to position it on the boss 35 and apply the nut 39 to the stud 37, the position of the rocker 7 prior to such replacement being as indicated by chain lines in FIGURE 4. Turning of the nut causes the teeth 29' on the arm 3 to be forced into engagement with the teeth 25 constituting part of the spindle 5, the inclined faces 27 and l 31 causing the teeth to register correctly and in so doing imparting a rotation to the spindle 5 and consequently causing the arm 3 to be automatically rotated through an angle of about 5 to 10, thereby bringing one set of contact points 19 on one side of said arm into compressed contact with one set of fixed points 21, as seen in FIG- URE 1. The rocker 7 has also been rotated through the same angle to assume the position shown in full lines in FIGURE 4, in which position of the mechanism the switch is ready for operation, having avoided the previous necessity for relieving any spring-loading transmitted to the contact arm before replacement could be effected.

I claim:

1. In an electric switch including a casing, a contact arm rotatably mounted in the casing, movable contact means moved by said arm adapted to engage relatively fixed contact means in the casing, means for rotating said contact arm through a rocker coaxial with said contact arm and moved by an actuator, and spring loading means eating between said actuator and said relatively fixed contacts urging said rocker toward a first limit position, the provision of, in combination, a coupling between said contact arm and said rocker whereby preliminary engagement may be effected between said contact arm and rocker without relieving the spring-loading, said coupling including first and second inclined cam means connected to said contact arm and first and second complementary inclined face means connected to said rocker, said contact arm being initially positionable on said rocker with said rocker at said first limit position and said fixed and mmable contact means in enagement and with only said first inclined cam means and first inclined face means in engagement, and means for axially urging the movable contact means automatically into spring urged electrical connection with said relatively fixed contact means against said spring-loading to partially rotate said rocker away from said first limit position and establish additional stress in said spring loading means and establish mutual seating of both said first and second inclined cam means on said first and second inclined face means, respectively.

2. An electric switch including a casing, a spindle rotatably mounted in the casing carrying a contact arm depending on one side of the casing and contacts loosely carried thereby adapted to engage fixed contacts for electrical connection with said loose contacts and means for rotating said contact arm through a rocker carried by said spindle on the other side of said casing and moved by a spring-loaded lever operated snap mechanism, in combination, a coupling between said contact arm and said spring-loaded rocker, comprisng teeth formed on said arm adapted to engage with similar teeth formed on a member constituting part of the said spindle carrying said arm and rocker, said interenga-ging teeth having inclined faces for causing the teeth to register and impart rotation to the said spindle on application of pressure to said contact arm, thereby rotating said arm automatically into its electrical connection with said contacts against said spring-loading, the spindle member in which the teeth are formed being provided with a cylindrical boss adapted to be engaged by an aperture in the contact arm for the purpose of locating the said interengaging teeth, [a threaded stud extending from said boss being adapted said inclined faces against said spring-loading.

References Cited in the file of this patent UNITED STATES PATENTS 1,136,557 Ross Apr. 20, 1915 2,038,554 Edgar Apr. 28, 1936 2,202,679 Woodin May 28, 1940 2,294,559 Ieflrey Sept. 1, 1942 2,390,365 Gofi Dec. 4, 1945 

1. IN AN ELECTRIC SWITCH INCLUDING A CASING, A CONTACT ARM ROTATABLY MOUNTED IN THE CASING, MOVABLE CONTACT MEANS MOVED BY SAID ARM ADAPTED TO ENGAGE RELATIVELY FIXED CONTACT MEANS IN THE CASING, MEANS FOR ROTATING SIAD CONTACT ARM THROUGH A ROCKER COAXIAL WITH SAID CONTACT ARM AND MOVED BY AN ACTUATOR, AND SPRING LOADING MEANS CATING BETWEEN SAID ACTUATOR AND SAID RELATIVELY FIXED CONTACTS URGING SAID ROCKER TOWARD A FIRST LIMIT POSITION, THE PROVISION OF, IN COMBINATION, A COUPLING BETWEEN SAID CONTACT ARM AND SAID ROCKER WHEREBY PRELIMINARY ENGAGEMENT MAY BE EFFECTED BETWEEN SAID CONTACT ARM AND ROCKER WITHOUT RELIEVING THE SPRING-LOADING, SAID COUPLING INCLUDING FIRST AND SECOND INCLINED CAM MEANS CONNECTED TO SAID CONTACT ARM AND FIRST AND SECOND COMPLEMENTARY INCLINED FACE MEANS CONNECTED TO SAID ROCKER, SAID CONTACT ARM BEING INITIALLY POSITIONABLE ON SAID ROCKER WITH SAID ROCKER AT SAID FIRST LIMIT POSITION AND SAID FIXED AND MOVABLE CONTACT MEANS IN ENAGEMENT AND WITH ONLY SAID FIRST INCLINED CAM MEANS AND FIRST INCLINED FACE MEANS IN ENGAGEMENT, AND MEANS FOR AXIALLY URGING THE MOVABLE CONTACT MEANS AUTOMATICALLY INTO SPRING URGED ELECTRICAL CONNECTION WITH SAID RELATIVELY FIXED CONTACT MEANS AGAINST SAID SPRING-LOADING TO PARTIALLY ROTATE SAID ROCKER AWAY FROM SAID FIRST LIMIT POSITION AND ESTABLISH ADDITIONAL STRESS IN SAID SPRING LOADING MEANS AND ESTABLISH MUTUAL SEATING OF BOTH SAID FIRST AND SECOND INCLINED CAM MEANS ON SAID FIRST AND SECOND INCLINED FACE MEANS, RESPECTIVELY. 